The program focusses on factors involved in the development of benign and malignant mammary and cervicovaginal lesions in mice. The objects of proposed studies include: The origin of inapparent transformed cells in normal mouse mammary tissues and the nature of cellular and host factors leading to their emergence as overt lesions. The presence of components of the MTV genome in DNA of mouse germline cells. Chemical carcinogen-induced transformation of rat mammary cells in vitro. Permeability and transport parameters of mammary tumor cell monolayers in culture on floating collagen gels. Influence of perinatal plus later treatment with steroid hormones on development of mammary and cervicovaginal tumors in mice and the sites of hormone action. Distortion of subsequent immune reactivity in mice given perinatal steroid treatment and the relation between immunologic changes and risk of neoplasia. Long-term effects on survival of mice after single-dose treatment with chemotherapeutic drugs. The role and fate of cellular factors responsible for epithelial cohesiveness in experimental invasion of other tissues by malignant mammary tumors. The influence of epithelial cell shape on hormone-induced secretory differentiation of mammary cells in culture.